1. Field of the Invention
This invention relates to an optical input device for a digital computer or terminal, but more particularly to a device made up of optical fibers forming a matrix to receive a light beam to indicate the position of the light beam as moves relative to the input device.
2. Description of the Prior Art
Prior art input devices include the mechanical mouse which involve wheels or rollers which maintain frictional contact with a surface. There are certain mechanical problems which are inherent with these mice, such as the problem in maintaining good frictional contact with a surface. If a mechanical mouse encounters a slippery portion of a surface, the resulting output signal will be inaccurate. Furthermore, a mechanical mouse uses a relatively large number of close tolerance parts and is difficult to make in mass production. Moreover, it is subject to mechanical "noise", such as lash and vibration, and requires frequent cleaning.
Another prior art input device is the joy stick control which includes a level, usually connected to a bearing. As the lever is moved and the bearing is rotated correspondingly, the bearing motion is sensed by potentiometers corresponding to different directions of bearing rotation. The output signal from a joy stick may be used for the same purpose as the output signal from a mouse. Both may be used to control a cursor. The distinguishing feature of a mouse is that two-dimensional motion over a surface corresponds directly with two-dimensional motion of a cursor in a graphic display.
More recently, optomechanical mice have been employed. As is the case with the mechanical mouse, the optomechanical mouse rolls a track ball over a surface in sense movement. Unlike the mechanical mouse, however, it incorporates optical encoders to measure distance. In the optical system, a shaft couples the movement to optical discs that interrupt a light beam as the ball moves. The design of the encoder wheel determines the resolution of the device.
More recently, optical mice have been used to input digital computers. This device must move over a pad with a special checker-board-pattern surface to gauge motion. The mouse contains one or two light-emitting diodes whose light shines onto the checker-board-pattern as the mouse moves. A mirror in the mouse shines light reflected from the surface into a light detector. The detector translates the light patterns into pulse trains that indicate motion. That indication of motion controls a cursor.
The fiber optics input device has advantages over any of these prior art devices:
1. There is no physical contact needed to activate the device and therefore there is no contact wear.
2. The fiber optics input device provides a non-electrical pad that is insensitive to electromagnetic and radio frequency fields, has a wide transmission bandwidth with low transmission loss, and eliminates any danger of combustion or sparking.
3. It is simple in design and therefore is of lower cost.
4. It is highly reliable.
5. It may be isolated in a hostile environment, including explosive fumes, high temperature, and high humidity.
6. It may be structured to measure distance from the light source to the device.